Abstract P2-03-10: A fit-for-purpose NGS system that reports ERBB2 (HER2) mutations and copy number variants for clinical trials research and drug development

Abstract

Introduction: HER2-positive breast cancers comprise 20-30% by subtype and represent the second poorest prognosis. In addition to HER2 signaling activation via protein overexpression or gene amplification (measured by IHC or ISH), somatic mutations in the ERBB2 (HER2) gene have been identified in 2-4% of breast cancers and reported to drive HER2 pathway signaling and tumorigenesis. Irreversible HER2 tyrosine kinase inhibitors such as neratinib have been shown to potently inhibit breast tumors harboring somatic HER2 activating mutations and are under active clinical investigation. A targeted molecular characterization strategy is thus needed to support clinical trial research. Here, we present an integrated NGS system that identifies multiple classes of ERBB2aberrations, including single nucleotide variants, insertion/deletion mutations, and copy number variations (CNVs). Methods: Genomic DNA was isolated from FFPE human tumor tissues or FFPE-embedded engineered cell lines expressing ERBB2 mutations. Pre-analytical sample QC was performed by a novel qPCR assay that quantifies amplifiable DNA templates suitable for library preparation. NGS libraries were prepared using the QuantideX® NGS ERBB2 Mutations assay, with two-pool PCR-based enrichment to detect multiple types of ERBB2 genomic alterations. Libraries were sequenced (Illumina MiSeq®) and analyzed using QuantideX® Reporter software, directly incorporating the pre-analytical QC data from each DNA sample to improve variant call accuracy. Results: The QuantideX® NGS ERBB2 Mutations system targets 28% of ERBB2 coding bases covering exons 8 and 17 - 24, including codons 713-989 of the tyrosine kinase domain. The assay also detects focal, whole-arm and polysomy-induced HER2 amplification using sentinel flanking amplicons, and amplicons covering CEN17 and copy number-neutral chromosomal regions identified in the TCGA breast cancer cohort. The assay was analytically validated in a CLIA-laboratory which included an analysis of 6 mixtures and titrations of synthesized DNA bearing 31 ERBB2 mutations, 17 engineered cell lines and FFPE cell-line blocks, and 12 surgically-resected FFPE carcinomas. A multi-day/operator study revealed 100% sensitivity and PPV for detection of ERBB2 SNVs, indels and complex variants down to 5% mutation positive in wild-type DNA. The NGS system was also used to profile ERBB2 variants in 473 FFPE human tumor tissues, including 280 breast carcinomas. Mutation-positive samples were confirmed by an orthogonal NGS method. A subset of 46 FFPE tissue samples were assessed for CNVs by NGS and compared with matched droplet digital PCR (ddPCR) analysis. A correlation of R2 > 0.91 between NGS and ddPCR underscores the potential of the assay to reveal both ERBB2 mutations and copy number changes. Conclusions: The QuantideX® NGS ERBB2system integrates optimized wet- and dry-bench elements to achieve broad and accurate detection of ERBB2 mutations and copy number variants from challenging FFPE specimens. The technology has the potential to advance breast cancer clinical research and aid in the selection of patients for clinical trials, particularly those that assess HER2-directed therapies such as afatinib, lapatinib, and neratinib. Citation Format: Zhu H, Zeigler R, Bridger S, Larson JL, Kincaid A, Cardwell R, Haynes BC, Andruss BF, Latham GJ. A fit-for-purpose NGS system that reports ERBB2 (HER2) mutations and copy number variants for clinical trials research and drug development [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-03-10.